With enough time and dedication, I wouldn't sell yourself short of any goal. Go for it. Be sure to set good short term and mid term goals too... for instance 7x5.25 for the STG and 8x5.75 for the MTG. Whatever works for you. That way you have something more reasonable to shoot for and obtain - it keeps the morale up.
The goal is not unreasonable, but you are probably looking at a long road ahead before you reach that. I agree about the short term goals, they give you something to shoot for in a shorter period of time, and you will maintain your motivation easier as you accomplish them. Otherwise, you might be so focused on your ultimate goal, that you don't fully appreciate what you've accomplished so far. For instance, when you reach 8, if all you are thinking about is that 9, then you'll be disappointed that you are an inch short of your goal, when you should be estatic that you are 1 1/2 inch past your start.